It is well known that when diesel fuel is at low temperatures approaching the cloud point, paraffin wax crystals will form. Further, at these cold temperatures, any water in the fuel tank may form ice crystals. To prevent wax or ice choking of the fuel system components, such as a filter, after a cold start, electric heaters are used in some prior art fuel delivery systems. Because newer diesel injection systems also have higher fuel supply and return flow for system cooling, the size of the electric heater becomes too large to have an adequate de-waxing or de-icing effect on the increased supply fuel flow. Therefore, it may be desirable to divert warm fuel from the injection system to the unfiltered side of the filter to de-wax or de-ice the filter after a cold start to unclog the filter and other fuel system components.
The inventors of the present invention have found that prior art temperature controlled recirculating systems, which are used to selectively divert warm fuel to the fuel filter to de-wax or de-ice the fuel filter during a cold start, generally do not adequately provide for de-waxing or de-icing close to the fuel inlet because these devices are located outside the fuel tank. This is primarily due to the fact that these devices are relatively large and would otherwise encompass too much space within the fuel tank. In addition, some of these devices do not adequately unclog the fuel filter because the recirculating devices are located remotely from the filter.